Method for the continuous production of optical fibre waveguides mounted in a thin-walled, radially closed metal tube

A method for the continuous production of a thin-walled, radially closed metal hollow profile with fibre waveguides mounted therein, the length of which exceeds the length of the metal hollow profile surrounding them, said method comprising the steps of:

• supplying a flat metal strip with a first supply speed to a deforming unit,
• continuously deforming the supplied flat metal strip to form a hollow profile with a slot running in a longitudinal direction, wherein two opposite edges of the metal strip are deformed to form the hollow profile lie flush against one another in a contact region extending in the longitudinal direction of the metal hollow profile, which edges are continuously welded to one another,
• wherein the edges for welding are led with the first supply speed past a welding region which is static in relation to a device which implements the method, and wherein a point in the welding region is heated by means of a laser,
• wherein, from a supply side of the metal hollow profile, one or more fibre waveguides from one or more fibre unwinders and a pre-warmed filler gel, the viscosity of which decreases with increasing temperature, are supplied such that, at the drawing-off side of the welding region, the one or more fibre waveguides lies or lie in the radially closed metal hollow profile in a manner embedded in the filler gel, wherein the supplied length of the fibres per unit of time is continuously determined,
• drawing off the welded metal hollow profile from the welding region,
• introducing a tensile force into the welded metal hollow profile by means of a draw-off capstan,
• wherein the metal hollow profile is elastically stretched and, in the stretched state, is led multiple times around the draw-off capstan, wherein the metal hollow profile and the filler gel cool further,
• wherein the tensile force acting on the metal hollow profile is monitored by means of a force measuring device, and wherein the elastic stretching of the metal hollow profile is eliminated when said metal hollow profile is supplied away from the draw-off capstan and to a receiving unit,
• measuring the length of the metal hollow profile that is led away from the draw-off capstan per unit of time, and
• receiving the metal hollow profile, with the fibre waveguide or fibre waveguides mounted therein, in the receiving unit,
• wherein a continuous determination of the ratios of length of the supplied fibre waveguide or of the supplied fibre waveguides and length of the metal hollow profile led away from the draw-off capstan, and a comparison with a specification value, are performed,
• wherein, furthermore, at least one controlled variable selected from a first list consisting of power of the laser, temperature of the filler gel, throughflow quantity of the filler gel per unit of time, tensile force exerted on the hollow profile and temperature of the hollow profile upstream of the draw-off capstan is recorded and, from this, for a continuous closed-loop control of the excess length of the fibre waveguide or of the fibre waveguides, at least one manipulated variable for a closed-loop control of a heater of a filler gel reservoir, and of a filling head is determined.